Landmark Study: 1 in 4 NFL Players Diagnosed With CTE After Death

Using conservative assumptions, researchers estimated CTE affected nearly one in four NFL players who died between 2015 and 2021, while dementia was also common overall.

John Rigolizzo

Published: 8/25/2026, 11:59:53 PM EDT

Landmark Study: 1 in 4 NFL Players Diagnosed With CTE After Death — A New York Jets helmet sits on an equipment case during the second half of an NFL preseason game against the Atlanta Falcons at Mercedes-Benz Stadium in Atlanta on Aug. 15, 2019. (Todd Kirkland/Getty Images)

A new study found that a concerning number of NFL players are developing chronic traumatic encephalopathy (CTE).

The landmark study, published in the British Medical Journal on Tuesday, found that nearly one in four players who died between 2015 and 2021 were diagnosed with some form of CTE.

"Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease that has been diagnosed in individuals with high exposure to repetitive head impacts," the study begins. "Like most neurodegenerative diseases, CTE can be definitively diagnosed only based on neuropathological evaluation after death... Because CTE can currently be diagnosed definitively only after death, the epidemiological features of CTE have been difficult to characterise. However, disease prevalence at death can be instructive, as it has been with other diseases informed by neuropathology, including neurodegenerative diseases, cerebrovascular diseases, and other disease processes."

Previous studies using data gathered from death certificates found that NFL players experience increased rates of dementia. One study cited by the researchers sampled records from more than 3,400 players with more than five seasons of play between 1959 and 1988; it found that the football players died from neurodegenerative diseases at a rate three times higher than the general U.S. population.

The study sampled 338 brains donated by deceased former football players, from a sample of 1,712 players who had died between 2008 and 2021. Of those 338 brains, 315 had been diagnosed with CTE. Using the most conservative assumptions—that only those 315 players who died, donated their brains, and were diagnosed with CTE actually had CTE—the disease had a prevalence of 18.5 percent. Under the least conservative assumptions—that all the remaining 1,374 deceased players who were not sampled in the study had CTE—the prevalence rate goes up to 98.7 percent.

Researchers also narrowed it down to the years 2015-2021, when brain donation became more common. In that time frame, 878 players died; 235 brains were donated. Of those brains, 215 were diagnosed with CTE. Under the most conservative assumptions—that those 215 brains were the only ones who had CTE—the prevalence rate was 24.5 percent, just under one in four. Using the least conservative assumptions—that the other 643 players all had CTE—the prevalence rate goes up to 97.7 percent.

The study also found the presence of other neurodegenerative diseases: 16.9 percent of cases had Lewy body disease; 15.1 percent had Alzheimer's; 6.8 percent had frontotemporal lobar degeneration; 3 percent had primary age-related tauopathy; and 2.4 percent had motor neuron disease, more commonly known as ALS (amyotrophic lateral sclerosis) or Lou Gehrig's disease. The study also found high rates of comorbidities associated with neurodegenerative diseases, including plaques, proteins, and vascular issues.

Dementia was also common among donors: 59.8 percent of donors had a dementia diagnosis; more than half of donors with stage III CTE also had dementia, and more than 90 percent of those with stage IV CTE had dementia. A dementia diagnosis was also linked to higher rates of neurodegenerative disease.

"Together, these findings indicate that NFL players have a higher prevalence of CTE at death than has been previously shown in multiple community based studies," the researchers concluded. "Furthermore, these data indicate that CTE severity at death is significantly associated with dementia in NFL player brain donors, and that dementia is common in these donors. Additional work is needed to further clarify the nature of this relation, particularly in other populations, with high lifetime exposure to repetitive head impacts."

Union Warns Players

The National Football League Players' Association responded to the study in an email to players, published in full by ProFootballTalk.

“Today, Massachusetts General Brigham and Boston University released a new study examining the prevalence of CTE among NFL players," the players' union said. "The findings are a sobering reminder that football carries serious risks that can have lasting consequences for players and their families. In short, the study suggests that CTE may be significantly more common among NFL players than previously understood, reinforcing the importance of continued research, care, and support."

The email noted that while CTE can only be diagnosed postmortem, there are early symptoms associated with the disease, including: memory issues; mood swings; depression; anxiety; sleep disturbances; and cognitive difficulties. The union urged players to receive a thorough medical evaluation.

“Research continues to improve our understanding of brain health and identify new ways to support players," the NFLPA said. "That is why the NFLPA has made major investments in brain health research and care with leading institutions such as the American Brain Foundation and the Football Players Health Study at Harvard University."

The union said the findings should be "a call to action across the entire football ecosystem." It promoted resources available to players and urged them to pay attention to their brain health and function, and get help early. The union also promised to hold conferences with medical experts to provide more information.